In general, a rotary electrical machine comprises a casing having inside a stator, rigidly connected to the casing, and a rotor, for example with permanent magnets, rotatably connected to the casing.
An example of a prior art electrical machine used as a reference for the present patent is described in the application WO20133008180 in the name of the same applicant.
An electronic module or electronic control module, connected to the stator, comprising a printed circuit and a plurality of active and passive electronic components forming a power section and a plurality of electronic signal components forming a control section, mounted on the printed circuit.
A cap closes the casing to form a closed container from which connection terminals protrude for the power supply and control connections of the control electronics.
The electrical machines used as reference for this invention are of the enclosed type known in particular as the sealed type, that is, sealed electrical machines.
One of the principle difficulties of the sealed type of electrical machine is the dispersal of the heat generated by the electronic module during operation of the electrical machine.
A solution designed to overcome this difficulty is described in the document already cited WO20133008180 in the name of the same applicant.
In this solution the cap of the electrical machine forms a transferring element, that is, a component for dispersing the heat generated by the electronic module; the power and signal electronic components are mounted on the side of the printed circuit facing the cap.
In addition, in this solution a thermally conductive paste is inserted between the electronic components and the cap so as to act as a dissipator thereby maximising the heat exchange between the cap and the components.
Today, the market specifies electrical machines, particularly those of the sealed type, which provide greater efficiency and higher power outputs than electrical machines of the known type and provide this higher performance in units of the same size.
The development of these high performance electrical machines has lead to the adoption, in the electronic drive module, of electronic power components with ever lower internal resistances. The purpose of this development is to limit the losses due to the Joule effect.
However, despite the relatively low internal resistance of the electronic power components, especially in high power applications (those with ratings of more than a kilowatt) and in applications with low voltage power supplies (operating with just a few volts), the circulating currents in the electronic power components can cause relatively high losses due to the Joule effect. A further basic design constraint is that the heat generated by each electronic power component must not decrease the efficiency of the electronic module of the machine.
The printed circuit in particular appears to be the weak link in the electronic module because its maximum operating temperature is lower than that of the electronic power components mounted and soldered onto the printed circuit itself.